Transport Requirement

Hi all, I'm new to Transports and need some help. at my client, the guy who worked before me, tried to transport some stuff from Dev to Q but he screwed up. Now I've been given that task, but dont know where to start. I mean how to check which objects i need to transport? Difference between first and subsequent transports of objects and stuff....please someone guide me and I will reward heavily too. My job's future depends on this task....

Farhan